A. Field of the Invention
The device of the present invention generally relates to molded case circuit breakers and, more particularly, to mechanisms for locking the handles of circuit breakers to prevent unauthorized operation thereof.
B. Description of the Prior Art
Circuit breakers and, more particularly molded case circuit breakers are old and well known in the prior art. Examples of such devices are disclosed in U.S. Pat. Nos. 2,186,251; 2,492,009; 3,239,638; 3,525,959; 3,590,325; 3,614,685; 3,775,713; 3,783,423; 3,805,199; 3,815,059; 3,863,042; 3,959,695; 4,077,025; 4,166,205; 4,258,403; and 4,295,025. In general, prior art molded case circuit breakers have been provided with movable contact arrangements and operating mechanisms designed to provide protection for an electrical circuit or system against electrical faults, specifically, electrical overload conditions, low level short circuit or fault current conditions, and, in some cases, high level short circuit or fault current conditions. Prior art devices have utilized an operating mechanism having a trip mechanism for controlling the movement of an over-center toggle mechanism to separate a pair of electrical contacts upon an overload condition or upon a short circuit or fault current condition. Such trip mechanisms have included a bimetal movable in response to an overload condition to rotate a trip bar, resulting in the movement of the over-center toggle mechanism to open a pair of electrical circuit breaker contacts. Such prior art devices have also utilized an armature movable in response to the flow of short circuit or fault current to similarly rotate the trip bar to cause the pair of contacts to separate. At least some prior art devices use blow-apart contacts to rapidly interrupt the flow of high level short circuit or fault currents. Typical prior art circuit breakers utilize manually engagable handles for moving separable electrical contacts into engagement and out of engagement and for resetting the contacts subsequently to a trip operation. Often, such manually engagable handles are operated from a remote location by means of an electrical operator. It is often desirable to lock the manually engageable handle or the electrical operator for the handle when the separable electrical contacts are out of engagement or in their OPEN position in order to prevent unauthorized or accidental use of the circuit breaker.
While many prior art devices have provided adequate protection against fault conditions in an electrical circuit, a need exists for dimensionally small molded case circuit breakers capable of fast, effective and reliable operation and, more specifically, for effective, inexpensive and reliable lock mechanisms to prevent the unauthorized use of electrical circuit breakers.